Mechanism

ABSTRACT

A returnable setback safety mechanism for fuzes of spin stabilized artillery in which the safety pin is depressed upon setback or rearward force exerted upon the mechanism. The safety pin will return to its original safety position after setback unless the mechanism is then subjected to projectile spin forces as a result of the projectile being launched.

[ Aug. 20, 1974 Emma iates Patent 1 Ranalli et al.

2,897,760 8/1959 Mott-Smith....................... l02/80 X 3,450,0496/1969 MECHANRSM [75] inventors: Nicholas J. Ranalli; James C.

both of Cornwells Heights,

Mount,

Primary ExaminerSamuel W. Engle Attorney, Agent, or Firm-Edward J.Kelly; Herbert Berl; William Sommer Army, Washington, DC.

Nov. 6, 1972 ABSTRACT [22] Filed:

[21] Appl' 303898 A returnable setback safety mechanism for fuzes ofspin stabilized artillery in which the safety pin is de- [52] U.S. preed upon setback or rearward force exerted upon the mechanism. The safetypin will return to its origi- [51] Int. Cl. F42c 15/20 102/78, 79, 80,7O

nal safety position after setback unless the mechanism is then subjectedto projectile spin forces as a result of the projectile being launched.

[58] Field of Search References Cited UNITED STATES PATENTS 2 Claims, 2Drawing Figures 2,448,228 8/1948 McCaslin et 102/80 X MECHANISM Theinvention described herein may be manufactured, used, and licensed by orfor the Government for governmental purposes without the payment to usof any royalty thereon.

This invention relates to mechanisms, and more particularly to a safetymechanism for artillery fuzes.

A non-returnable setback safety mechanism may become locked in an armedcondition if dropped from above a predetermined height whereby themechanism will have its effectiveness limited because it will arm andlose its safety function at relatively low setback G values. 7 It is anobject of the invention to provide a setback safety mechanism in whichthe safety pin is positively returned to a safe unarming position unlessthe setback force is immediately followed by a predetermined amount ofsustained artillery spin.

Another object of the invention is to provide such a mechanism in whichsafety and reliability are enhanced.

These and other objects, features and advantages will become moreapparent from the following description and accompanying drawings inwhich:

FIG. 1 is longitudinal sectional view of a spin stabilized artilleryfuze safety mechanism embodying the principles of the invention.

FIG. 2 is a view similar to FIG. 1 wherein the mechanism has beensubjected to sequential setback and sustained artillery spin forces asin the launching of a projectile.

The safety pin 11 of the returnable setback safety mechanism showngenerally at (FIG. 1), normally extends in the path of an unarmed rotorbody 12 of a spin stabilized artillery fuze mechanism to prevent therotor body 12 carrying detonator 13 from rotating about its own journalmeans (not shown) to move the detonator to an armed position where itwill be exposed to an appropriate ignition means or firing pinarrangement. The rotor body journal axis is parallel to the longitudinalspin axis 14 of the fuze mechanism so that the rotor body 12 can rotatein a plane normal to spin axis 14 for movement to its armed positionwhen safety pin 11 is held in a depressed condition (FIG. 2) as will behereinafter described. The pin 11 normally extends along the centerline15 of the safety mechanism which is parallel to and axially offset fromthe spin axis 14.

The safety mechanism has a screw body 16 provided with external threads17 by which it is suitably secured within the fuze mechanism, aforwardly opening cylindrical recess 18 in which is seated compressionspring 19 that normally biases forwardly the head 20 on the rearmost endof pin 11, and an enlarged forwardmost recess 21 by which the covermember 22 can be secured, as by staking, to the forward end of the screwbody. The cover 22 is centrally apertured to normally receive the shaftof pin 11 and has a conical ramp surface 23 on its rearward internalportion to facilitate return of safety pin 11 to its normal safeposition should the safety mechanism be subjected to a setback forcewithout any accompanying spin forces. To this end the forward portion ofsafety pin 11 is provided with a hemispherical tip 24 which is directedor cammed by the ramp surface 23 through the central aperture of thecover 22 when the spring is extended after being compressed. The screwbody recess 18 is defined by a cylindrical wall having a diameter lessthan the periphery of the cover 22 and preferably slightly greater thanthe periphery of the conical ramp surface 23. The safety pin 11 of thesetback safety mechanism is positively returned to the FIG. 1 safeunarming position unless the setback force is immediately followed by apredetermined amount of sustained artillery spin.

Upon firing of the artillery projectile, the safety pin 11 firstexperiences setback and compresses the spring 19 to solid height. Beforesetback ceases, projectile spin forces the pin 11 against the screw bodyrecess wall 18 (FIG. 2). When setback ceases after launch, projectiledeceleration and spring bias act on the pin 11 to tend to urge it towardits safe unarming position. However, the projectile is still spinningand the normal force between the pin and the screw body recess wallgenerates sufficient friction to prevent the pin 11 to return throughthe cover aperture, thus enabling rotation of rotor body to an armingposition as controlled by a fuze timing mechanism (not shown).

Various modifications, changes or alterations may be resorted to withoutdeparting from the scope of the invention as defined in the appendedclaims.

We claim:

1. In a spin stabilized artillery device having a rotor body adapted tomove in a predetermined plane substantially perpendicular to theartillery longitudinal spin axis,

a returnable safety mechanism having a pin member normally extendingparallel to and axially offset from said spin axis and in the path ofsaid body to prevent movement thereof, said safety mechanism including ascrew body having a forwardly opening recess, said pin member having alongitudinal body portion and a head portion at its rearmost end, saidbody portion being of a diameter smaller than said head portion and bothsaid body and head portions having a diameter smaller than said recessto enable pivoting of said pin member in said recess, a compressionspring seated in said recess and engaging said pin head to normally biassaid pin forwardly into said path, and a cover member secured to aforward portion of said screw body, said cover member having a forwardsurface with a central aperture for normally receiving said pin memberand a rearward internal surface portion forming a conical ramp over asubstantial portion thereof for assuringly directing and returning aforward portion of said pin member through said aperture when saidcompression spring is extended after being compressed to the extent thatsaid pin member has been withdrawn from said cover aperture as a resultof a set back force received by said pin member unaccompanied by anysustained centrifugal force thereto, said pin member having asubstantially hemispherical forwardmost tip.

2. The structure according to claim 1 wherein said screw body recess isdefined by a substantially cylindrical wall within said screw body, saidcylindrical wall having a diameter less than said the periphery of saidcover and slightly greater than the periphery of said conical surface.

1. In a spin stabilized artillery device having a rotor body adapted tomove in a predetermined plane substantially perpendicular to theartillery longitudinal spin axis, a returnable safety mechanism having apin member normally extending parallel to and axially offset from saidspin axis and in the path of said body to prevent movement thereof, saidsafety mechanism including a screw body having a forwardly openingrecess, said pin member having a longitudinal body portion and a headportion at its rearmost end, said body portion being of a diametersmaller than said head portion and both said body and head portionshaving a diameter smaller than said recess to enable pivoting of saidpin member in said recess, a compression spring seated in said recessand engaging said pin head to normally bias said pin forwardly into saidpath, and a cover member secured to a forward portion of said screwbody, said cover member having a forward surface with a central aperturefor normally receiving said pin member and a rearward internal surfaceportion forming a conical ramp over a substantial portion thereof forassuringly directing and returning a forward portion of said pin memberthrough said aperture when said compression spring is extended afterbeing compressed to the extent that said pin member has been withdrawnfrom said cover aperture as a result of a set back force received bysaid pin member unaccompanied by any sustained centrifugal forcethereto, said pin member having a substantially hemisphericalforwardmost tip.
 2. The structure according to claim 1 wherein saidscrew body recess is defined by a substantially cylindrical wall withinsaid screw body, said cylindrical wall having a diameter less than saidthe periphery of said cover and slightly greater than the periphery ofsaid conical surface.